build: add checksum target

Add a new "checksum" make target which generates an sha256sums file over the
image files produced in bin/targets/ and automatically call it during make
world after the package index generation.

The advantage of this new target is that it is guaranteed to run after the
images, the SDK and the ImageBuilder archives have been generated to ensure
that they all end up in the checksum file. Fixes FS#51.

Uses sed to postprocess the OpenSSL digest output into an sha256sum command
compatible format.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

Makefile

@@ -83,9 +83,13 @@ prereq: $(target/stamp-prereq) tmp/.prereq_packages
 		exit 1; \
 	fi
 
+checksum: FORCE
+	$(call sha256sums,$(BIN_DIR))
+
 prepare: .config $(tools/stamp-install) $(toolchain/stamp-install)
 world: prepare $(target/stamp-compile) $(package/stamp-compile) $(package/stamp-install) $(target/stamp-install) FORCE
 	$(_SINGLE)$(SUBMAKE) -r package/index
+	$(_SINGLE)$(SUBMAKE) -r checksum
 
 .PHONY: clean dirclean prereq prepare world package/symlinks package/symlinks-install package/symlinks-clean
 

rules.mk

@@ -371,6 +371,13 @@ define file_copy
 	$(CP) $(1) $(2)
 endef
 
+# Calculate sha256sum of any plain file within a given directory
+# $(1) => Input directory
+define sha256sums
+	(cd $(1); find . -maxdepth 1 -type f -not -name 'sha256sums' -printf "%P\n" | sort | \
+		xargs openssl dgst -sha256 | sed -ne 's!^SHA256(\(.*\))= \(.*\)$$!\2 *\1!p' > sha256sums)
+endef
+
 # file extension
 ext=$(word $(words $(subst ., ,$(1))),$(subst ., ,$(1)))
 

target/imagebuilder/files/Makefile

@@ -125,6 +125,7 @@ ifneq ($(USER_FILES),)
 endif
 	$(MAKE) package_postinst
 	$(MAKE) build_image
+	$(MAKE) checksum
 
 package_index: FORCE
 	@echo
@@ -170,6 +171,11 @@ build_image: FORCE
 	$(NO_TRACE_MAKE) -C target/linux/$(BOARD)/image install TARGET_BUILD=1 IB=1 EXTRA_IMAGE_NAME="$(EXTRA_IMAGE_NAME)" \
 		$(if $(USER_PROFILE),PROFILE="$(USER_PROFILE)")
 
+checksum: FORCE
+	@echo
+	@echo Calculating checksums...
+	@$(call sha256sums,$(BIN_DIR))
+
 clean:
 	rm -rf $(TMP_DIR) $(DL_DIR) $(TARGET_DIR) $(BIN_DIR)